Excerpted from AVMA Disease Risks for Dogs and the WSAVA Publication "Vaccination Guidelines for the Owners and the Breeders of Dogs and Cats," 2010
Kennel cough or canine respiratory disease complex (CRDC), is caused by a combination of viruses and bacteria. This complex may involve infection with canine adenovirus type 2, canine parainfluenza 2, Bordetella bronchiseptica and other bacteria (e.g. Streptococcus and Mycoplasma species). In addition, anatomic and environmental factors such as shape of nose, ventilation, humidity, dust, poor hygiene and particularly stress are important in development of this disease. Kennel cough is very contagious. Dogs become infected by coming into contact with an infected dog. Dogs with kennel cough may not seem ill in the early stages of the disease but they can still infect other dogs. Most commonly, dogs with kennel cough will have a snotty nose and a dry, hacking cough. Vaccination for kennel cough is based on risk of exposure.